1. Field of the Invention
The present invention relates to an objective and to an assembling method for it.
2. Description of the Related Art
An objective is usually designed so that a desired performance is achieved using a plurality of lenses. However, when a plurality of lenses which were manufactured in accordance with a design are actually assembled, the desired performance is sometimes not achieved due to manufacturing errors and the like in the thickness and the curvature of the lenses, which occur in the manufacturing process.
In objective assembling processes, therefore, in order to suppress performance degradations due to manufacturing errors or the like, various adjustments are generally performed, such as an eccentricity adjustment for adjusting the eccentricity of lenses and an interval adjustment for adjusting the intervals between lenses.
As an example, Japanese Laid-open Patent Publication No. 2009-53339 discloses a method in which a force is applied to a lens frame (an inner frame) by inserting an adjustment screw into an adjustment hole (a threaded hole) provided at the housing (the outer frame) of an objective, thereby adjusting the eccentricity of the lens.
By performing various adjustments including such an eccentricity adjustment, desired performances of an objective can be achieved.
Japanese Laid-open Patent Publication No. 2009-53339 discloses the configuration of an objective in which lenses and separation rings (interval rings) are alternately arranged along the optical axis within a housing and a female thread at the housing and a male thread at a pressing ring are screwed together so that the pressing ring fixes the lenses and the separation rings.
In regard to the objective disclosed in Japanese Laid-open Patent Publication No. 2009-53339, lenses and separation rings apply optical-axis-direction forces to each other using a holding force received from the pressing ring, and therefore they are fixed at predetermined positions within the housing. In other words, the lenses are not individually fixed within the housing, but all of the lenses are collectively held and fixed within the housing.